The field of application of the invention lies in particular with gas turbine aeroengines. Nevertheless, the invention is applicable to other turbine engines, e.g. industrial turbines.
Ceramic matrix composite (CMC) materials are known for conserving their mechanical properties at high temperatures, which makes them suitable for constituting hot structural elements.
In gas turbine aeroengines, improving efficiency and reducing certain polluting emissions lead to seeking operation at ever higher temperatures. With turbine ring assemblies that are made entirely out of metal, it is necessary to cool all of the elements of the assembly and in particular the turbine ring that is subjected to very hot streams, typically at temperatures higher than the temperature that can be withstood by the metal material. Such cooling has a significant impact on the performance of the engine, since the cooling stream used is taken from the main stream through the engine. In addition, the use of metal for the turbine ring limits potential for increasing temperature in the turbine, even though that would make it possible to improve the performance of aeroengines.
That is why it has already been envisaged to make use of CMC for various hot portions of engines, particularly since CMCs present the additional advantage of density that is lower than that of the refractory metals conventionally used.
Thus, making single-piece turbine ring sectors out of CMC is described in particular in Document US 2012/0027572. The ring sectors comprise an annular base having an inner face defining the inside face of the turbine ring and an outer face from which there extend two tab-forming portions having their ends engaged in housings of a metal structure of the ring support.
The use of CMC ring sectors makes it possible to reduce significantly the amount of ventilation needed for cooling the turbine ring. Nevertheless, holding ring sectors in position remains a problem, in particular in the face of differential expansion that can occur between the metal support structure and the CMC ring sectors. In addition, another problem lies in the stresses generated by the imposed movements. Furthermore, ring sectors need to be held in position even in the event of contact between the tip of a blade of a rotor wheel and the inside faces of the ring sectors.